A disk storage system may include a redundant array of inexpensive disks (RAID) sub-system. The RAID sub-system may store an aggregation of data referred to as a “strip” located on each of several data disk drives included in the RAID sub-system. Each strip from each of the data disk drives may be related to the others by a parity strip located on one of the several data disk drives or on a separate parity disk drive. The parity strip and the related data strips may be referred to collectively as a “stripe.”
The parity strip may be calculated by performing an exclusive OR operation on the related data strips, and it may be used by the RAID sub-system together with the data strips to recalculate the value of a data strip that becomes unreadable at some time after writing the stripe. A redundancy may thus be incorporated into the RAID sub-system, and the redundancy may enable recovery of a volume following one or more disk drive failures (“degraded mode” of operation). A problem may arise, however, if a processor or controller performing a write update to a target data strip or to the parity strip resets unexpectedly while operating in the degraded mode. The unexpected reset could be triggered by a power loss or a fatal operating system error, for example. The parity strip may be inconsistent with the data strips in the stripe following the reset.